The present invention concerns cutting large sheet material workpieces. For many years this process has been carried out by means of punch presses, by the use of punch and die sets. The punch and die sets are often mounted in respective turret holders, which move a selected punch and die set to a punching station. The workpiece is supported on a large table and transported by means of a carriage mechanism having grippers holding the workpiece to move the sheet so as to bring a selected location whereat a particular hole is to be formed to the punching station.
In some instances, large or contoured openings or edge contours are required, which in some instances could not be carried out by use of punch and die sets. In other situations, the tooling costs would be excessive.
Such openings may be formed by a nibbling operation, in which successive punching along a line as the workpiece is moved past the punching station forms the contoured opening, but slight scalloping of the edge results, which is sometimes unacceptable.
In more recent years, laser contour cutting of such workpieces has been employed in which a powerful laser beam is directed through the workpiece as the workpiece is transported along a selected path.
Another known approach involves plasma arc cutting, in which a plasma arc is generated similarly directed through the workpiece to cut a line as the workpiece is moved past the arc.
Such laser and plasma arc cutting is capable of forming almost any contour shape and eliminates the need for high cost special punches and dies.
There has also been heretofore provided a hybrid combination of a punch press and a laser beam cutting head as well as a hybrid combination of a punch press with a plasma arc cutting head.
In these hybrid punch presses, the laser beam or plasma arc cutting head is positioned at a fixed offset to the punching station. The CNC controls appropriately move the workpiece with respect to the offset location in executing the contoured cutting of the workpiece.
At the location of the laser or plasma arc cutting station, a discharge chute and/or dust collector must be provided to receive the discharging beam or arc and to collect the slag and exhaust the gases incidental to the cutting process. Cutting with a laser beam and plasma arc have respective advantages and disadvantages. The plasma arc has a higher cutting speed and cuts through a wide variety of metal such as aluminum, stainless steel, brass, and steel. The plasma arc also has the capability of cutting relatively thick material.
The disadvantages include the fact that the kerf is wider, and the kerf angle is greater. More slag is produced, and the accuracy of cutting is not as good as the laser beam.
The laser beam, on the other hand, has the advantage of being very clean and accurate and has a narrower, straighter kerf and cuts materials other than metal, i.e., plastic, wood, composite, etc.
The disadvantage of the laser beam is it has a slower cutting speed, a higher energy consumption, it is more difficult to cut thick material and more difficult to cut certain metal materials, i.e., stainless steel, aluminum, and brass.
In order to have access to the respective capabilities of each device, it has heretofore been required to purchase both types of equipment incurring the high cost of both types of equipment and the need for floor space for both presses.